There has been an increased interest in metal-oxide-semiconductor field-effect transistors (MOSFETs) incorporating substrates having a (110) surface orientation, particularly with respect to PMOS devices. This interest is due to the increased (approximately 2×) hole mobility advantage as compared to traditional (100) devices as well as the ever-increasing importance of (110) channels in advanced FET structures, such as FinFETs, Tri-gate FETs, and the like.
Known (110) pMOSFET (pMOS, or pFET) devices, however, are unsatisfactory in a number of respects. For example, such devices exhibit an unexpectedly high source-drain external resistance (Rext). This resistance penalty substantially limits drive current, in some cases by 20%, and thus presents a significant barrier to achieving high drive current and high performance in (110) PMOS devices.
There is therefore a long-felt need for MOSFET structures that can leverage the higher hole mobility advantages of (110) substrates while avoiding the increased external resistance associated therewith. These and other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.